The meteorite that exploded over Chelyabinsk Russia in February most likely collided with another heavenly body or had a close encounter with the Sun before falling to Earth.
An Institute of Geology and Mineralogy (IGM) team examined tiny pieces of the meteorite, and noticed they had gone through an "intense melting process" in the past, a European Association of Geochemistry press release reported. This event occurred before the meteorite disintegrated in Earth's atmosphere.
"The meteorite which landed near Chelyabinsk is a type known as an LL5 chondrite and it's fairly common for these to have undergone a melting process before they fall to Earth," Dr. Victor Sharygin from IGM, said. "This almost certainly means that there was a collision between the Chelyabinsk meteorite and another body in the solar system or a near miss with the Sun."
The research team divided the meteorite fragments into three categories: light, medium, and dark. The darkest pieces are from where the meteorite came closest to Earth.
The dark material is made up of a "fine grained material" that endured an extreme process of melting. The grainy material differs from "fusion crust," which forms when melted areas of the meteorite solidify when it enters the Earth's atmosphere.
"Of the many fragments we've been analyzing, only three dark samples show strong evidence of earlier metamorphism and melting," Dr. Sharygin, said. "However, many fragments of the meteorite were picked up by members of the public, so it's impossible to say how large a portion of the meteorite was affected. We hope to find out more once the main body of the meteorite is raised from Chebarkul Lake."
The team made another unusual discovery. Traces of platinum elements were found in the fusion crust of certain meteorite fragments. These elements would not be able to accumulate in the short period of time it takes to form a fusion crust.
"Platinum group elements usually occur as trace elements dispersed in meteorite minerals, but we found them as a nanometer-sized mineral (100-200 nm) in a metal-sulfide globule in the fusion crust of the Chelyabinsk meteorite," Dr. Sharygin, said. "We think the appearance (formation) of this platinum group mineral in the fusion crust may be linked to compositional changes in metal-sulfide liquid during remelting and oxidation processes as the meteorite came into contact with atmospheric oxygen."
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